We† provide an overview of the Model Based Systems Engineering (MBSE) language, tool, and methodology being used in our development of the Operational Plan for Large Synoptic Survey Telescope (LSST) operations. LSST’s Systems Engineering (SE) team is using a model-based approach to operational plan development to: 1) capture the topdown stakeholders’ needs and functional allocations defining the scope, required tasks, and personnel needed for operations, and 2) capture the bottom-up operations and maintenance activities required to conduct the LSST survey across its distributed operations sites for the full ten year survey duration. To accomplish these complimentary goals and ensure that they result in self-consistent results, we have developed a holistic approach using the Sparx Enterprise Architect modeling tool and Systems Modeling Language (SysML). This approach utilizes SysML Use Cases, Actors, associated relationships, and Activity Diagrams to document and refine all of the major operations and maintenance activities that will be required to successfully operate the observatory and meet stakeholder expectations. We have developed several customized extensions of the SysML language including the creation of a custom stereotyped Use Case element with unique tagged values, as well as unique association connectors and Actor stereotypes. We demonstrate this customized MBSE methodology enables us to define: 1) the rolls each human Actor must take on to successfully carry out the activities associated with the Use Cases; 2) the skills each Actor must possess; 3) the functional allocation of all required stakeholder activities and Use Cases to organizational entities tasked with carrying them out; and 4) the organization structure required to successfully execute the operational survey. Our approach allows for continual refinement utilizing the systems engineering spiral method to expose finer levels of detail as necessary. For example, the bottom-up, Use Case-driven approach will be deployed in the future to develop the detailed work procedures required to successfully execute each operational activity.

This paper describes the status and details of the large synoptic survey telescope<sup>1,2,3</sup> mount assembly (TMA). On June 9<sup>th</sup>, 2014 the contract for the design and build of the large synoptic survey telescope mount assembly (TMA) was awarded to GHESA Ingeniería y Tecnología, S.A. and Asturfeito, S.A. The design successfully passed the preliminary design review on October 2, 2015 and the final design review January 29, 2016. This paper describes the detailed design by subsystem, analytical model results, preparations being taken to complete the fabrication, and the transportation and installation plans to install the mount on Cerro Pachón in Chile. This large project is the culmination of work by many people and the authors would like to thank everyone that has contributed to the success of this project.

This paper reports on the early investigation of using the work flow model for observatory infrastructure software. We researched several work ow engines and identified 3 for further detailed, study: Bonita BPM, Activiti and Taverna. We discuss the business process model and how it relates to observatory operations and identify a path finder exercise to further evaluate the applicability of these paradigms.

This paper reports on progress and plans for all meta-components of the Large Synoptic Survey Telescope (LSST) observatory control system (OCS). After an introduction to the scope of the OCS we discuss each meta- component in alphabetical order: application, engineering and facility database, maintenance, monitor, operator- remote, scheduler, sequencer, service abstraction layer and telemetry. We discuss these meta-components and their relationship with the overall control and operations strategy for the observatory. At the end of the paper, we review the timeline and planning for the delivery of these items.

Construction of the Large Synoptic Survey Telescope system involves several different organizations, a situation that poses many challenges at the time of the software integration of the components. To ensure commonality for the purposes of usability, maintainability, and robustness, the LSST software teams have agreed to the following for system software components: a summary state machine, a manner of managing settings, a flexible solution to specify controller/controllee relationships reliably as needed, and a paradigm for responding to and communicating alarms. This paper describes these agreed solutions and the factors that motivated these.

The LSST communications middleware is based on a set of software abstractions; which provide standard interfaces for common communications services. The observatory requires communication between diverse subsystems, implemented by different contractors, and comprehensive archiving of subsystem status data. The Service Abstraction Layer (SAL) is implemented using open source packages that implement open standards of DDS (Data Distribution Service1) for data communication, and SQL (Standard Query Language) for database access. For every subsystem, abstractions for each of the Telemetry datastreams, along with Command/Response and Events, have been agreed with the appropriate component vendor (such as Dome, TMA, Hexapod), and captured in ICD's (Interface Control Documents).The OpenSplice (Prismtech) Community Edition of DDS provides an LGPL licensed distribution which may be freely redistributed. The availability of the full source code provides assurances that the project will be able to maintain it over the full 10 year survey, independent of the fortunes of the original providers.

The Large Synoptic Survey Telescope (LSST) is a complex system of systems with demanding performance and operational requirements. The nature of its scientific goals requires a special Observatory Control System (OCS) and particularly a very specialized automatic Scheduler. The OCS Scheduler is an autonomous software component that drives the survey, selecting the detailed sequence of visits in real time, taking into account multiple science programs, the current external and internal conditions, and the history of observations. We have developed a SysML model for the OCS Scheduler that fits coherently in the OCS and LSST integrated model. We have also developed a prototype of the Scheduler that implements the scheduling algorithms in the simulation environment provided by the Operations Simulator, where the environment and the observatory are modeled with real weather data and detailed kinematics parameters. This paper expands on the Scheduler architecture and the proposed algorithms to achieve the survey goals.

The Large Synoptic Survey Telescope project was an early adopter of SysML and Model Based Systems Engineering
practices. The LSST project began using MBSE for requirements engineering beginning in 2006 shortly after the initial
release of the first SysML standard. Out of this early work the LSST’s MBSE effort has grown to include system
requirements, operational use cases, physical system definition, interfaces, and system states along with behavior
sequences and activities. In this paper we describe our approach and methodology for cross-linking these system
elements over the three classical systems engineering domains – requirement, functional and physical - into the LSST
System Architecture model. We also show how this model is used as the central element to the overall project systems
engineering effort. More recently we have begun to use the cross-linked modeled system architecture to develop and
plan the system verification and test process. In presenting this work we also describe “lessons learned” from several
missteps the project has had with MBSE. Lastly, we conclude by summarizing the overall status of the LSST’s System
Architecture model and our plans for the future as the LSST heads toward construction.

The Dark Energy Camera (DECam) is a new 520 Mega Pixel CCD camera with a 3 square degree field of view built for
the Dark Energy Survey (DES). DECam is mounted at the prime focus of the Blanco 4-m telescope at the Cerro-Tololo
International Observatory (CTIO). DES is a 5-year, high precision, multi-bandpass, photometric survey of 5000 square
degrees of the southern sky that started August 2013. In this paper we briefly review SISPI, the data acquisition and
control system of the Dark Energy Camera and follow with a discussion of our experience with the system and the
lessons learned after one year of survey operations.

In preparation for the arrival of the Dark Energy Camera (DECam) at the CTIO Blanco 4-m telescope, both the hardware
and the software of the Telescope Control System (TCS) have been upgraded in order to meet the more stringent
requirements on cadence and tracking required for efficient execution of the Dark Energy Survey<sup>1</sup>. This upgrade was
also driven by the need to replace obsolete hardware, some of it now over half a century old.
In this paper we describe the architecture of the new mount control system, and in particular the method used to develop
and implement the servo-driver portion of the new TCS. This portion of the system had to be completely rethought,
when an initial approach, based on commercial off the shelf components, lacked the flexibility needed to cope with the
complex behavior of the telescope. Central to our design approach was the early implementation of extensive telemetry,
which allowed us to fully characterize the real dynamics of the telescope. These results then served as input to extensive
simulations of the proposed new servo system allowing us to iteratively refine the control model. This flexibility will be
important later when DECam is installed, since this will significantly increase the moving mass and inertia of the
telescope.
Based on these results, a fully digital solution was chosen and implemented. The core of this new servo hardware is
modern cRIO hardware, which combines an embedded processor with a high-performance FPGA, allowing the
execution of LabVIEW applications in real time.

The Dark Energy Camera (DECam) has been installed on the V. M. Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. This major upgrade to the facility has required numerous modifications to the telescope and improvements in observatory infrastructure. The telescope prime focus assembly has been entirely replaced, and the f/8 secondary change procedure radically changed. The heavier instrument means that telescope balance has been significantly modified. The telescope control system has been upgraded. NOAO has established a data transport system to efficiently move DECam's output to the NCSA for processing. The observatory has integrated the DECam highpressure, two-phase cryogenic cooling system into its operations and converted the Coudé room into an environmentally-controlled instrument handling facility incorporating a high quality cleanroom. New procedures to
ensure the safety of personnel and equipment have been introduced.

The Large Synoptic Survey Telescope (LSST) is a project envisioned as a system of systems with demanding science,
technical, and operational requirements, that must perform as a fully integrated unit. The design and implementation of
such a system poses big engineering challenges when performing requirements analysis, detailed interface definitions,
operational modes and control strategy studies. The OMG System Modeling Language (SysML) has been selected as the
framework for the systems engineering analysis and documentation for the LSST. Models for the overall system
architecture and different observatory subsystems have been built describing requirements, structure, interfaces and
behavior. In this paper we show the models for the Observatory Control System (OCS) and the Telescope Control
System (TCS), and how this methodology has helped in the clarification of the design and requirements. In one common
language, the relationships of the OCS, TCS, Camera and Data management subsystems are captured with models of the
structure, behavior, requirements and the traceability between them.

The Large Synoptic Survey Telescope is a complex hardware - software system of systems, making up a highly
automated observatory in the form of an 8.4m wide-field telescope, a 3.2 billion pixel camera, and a peta-scale data
processing and archiving system. As a project, the LSST is using model based systems engineering (MBSE)
methodology for developing the overall system architecture coded with the Systems Modeling Language (SysML).
With SysML we use a recursive process to establish three-fold relationships between requirements, logical & physical
structural component definitions, and overall behavior (activities and sequences) at successively deeper levels of
abstraction and detail. Using this process we have analyzed and refined the LSST system design, ensuring the
consistency and completeness of the full set of requirements and their match to associated system structure and
behavior. As the recursion process proceeds to deeper levels we derive more detailed requirements and specifications,
and ensure their traceability. We also expose, define, and specify critical system interfaces, physical and information
flows, and clarify the logic and control flows governing system behavior. The resulting integrated model database is
used to generate documentation and specifications and will evolve to support activities from construction through final
integration, test, and commissioning, serving as a living representation of the LSST as designed and built. We discuss
the methodology and present several examples of its application to specific systems engineering challenges in the LSST
design.

The SOAR telescope fast tip-tilt tertiary mirror, was delivered by the Goodrich Optical and Space Systems Division,
Danbury, CT, and integrated into the SOAR optical system in 2004. It consist of a plane, light weighted 655&times;470 mm
elliptical mirror, controllable over a range of ±1 mrad, in two axes, with a required position loop bandwidth of 50 Hz. It
operates using the signal from a fast read-out guide camera to generate position commands, in an outer loop fashion.
The original tertiary mirror controller consisted of several analog circuit boards, incorporating the position control loop
compensation, and power amplifiers. This system was limited by the difficulty of making any modifications, to optimize
the control loop, and meet the required bandwidth. The analog controller was replaced with a digital controller based on
a National Instruments Compact RIO/FPGA device. This allows the full optimization of the control system, and also
allows closing the torque (acceleration) loop using the optical feedback of the guide signal alone, which should result in
even higher performance. This paper will describe the models, design, and performance tests, of the new digital control
system.

The Blanco 4-meter telescope has been in operation for over 30 years and is now subject to an extensive upgrade of its
control system, both of the hardware and software aspects. The motivation for the upgrade, besides the normal
replacement of obsolete components, is the preparation of the telescope for the installation of the DECAM instrument,
which makes greater operational demands than can't be met by the current system. The architecture of the new system is
in line with the designs proposed for modern telescopes like the Large Synoptic Survey Telescope (LSST), and its
implementation utilizes similar technologies as proposed for that project. In this paper we present a detailed description
of the upgraded system, including tape encoders, control algorithms, the use of trajectories to optimize motions,
communications middleware, and its performance as a whole.

The LSST middleware design is based on a set of software abstractions; which provide standard interfaces for common communications services. The observatory requires communication between many subsystems, and comprehensive archiving of subsystem status data. Control commands as well as health and status data from across the observatory must be stored to support both the science data analysis, and trending analysis for the early detection of hardware anomalies.
The Service Abstraction Layer (SAL) is implemented using open source packages that implement open standards of DDS (Data DistributionService) for data communication and SQL for storage.
Designs for the automatic generation of code, documentation, and subsystem simulation, are being developed. Abstractions for the Telemetry datastreams, each with customized data structures, Command/Response, and the Logging and Alert messages are described.

In this paper we describe the data acquisition and control system of the Dark Energy Camera (DECam),
which will be the primary instrument used in the Dark Energy Survey (DES). DES is a high precision multibandpath
wide area survey of 5000 square degrees of the southern sky. DECam currently under construction
at Fermilab will be a 3 square degree mosaic camera mounted at the prime focus of the Blanco 4m telescope
at the Cerro-Tololo International Observatory (CTIO). The DECam data acquisition system (SISPI) is
implemented as a distributed multi-processor system with a software architecture built on the Client-Server
and Publish-Subscribe design patterns. The underlying message passing protocol is based on PYRO, a
powerful distributed object technology system written entirely in Python. A distributed shared variable
system was added to support exchange of telemetry data and other information between different components
of the system. In this paper we discuss the SISPI infrastructure software, the image pipeline, the observer
interface and quality monitoring system, and the instrument control system.

The Dark Energy Survey (DES) is a 5000 square degree survey of the southern galactic cap set to take place
on the Blanco 4-m telescope at Cerra Tololo Inter-American Observatory. A new 500 MP camera and control
system are being developed for this survey. To facilitate the data acquisition and control, a new user interface
is being designed that utilizes the massive improvements in web based technologies in the past year. The work
being done on DES shows that these new technologies provide the functionality and performance required to
provide a productive and enjoyable user experience in the browser.

The Large Synoptic Survey Telescope (LSST) is a project with stringent requirements on the control aspects and
telemetry capture demands, to command the cadence of the survey process, and to help analyze and discover the
systematics of the observing process. For that purpose, the Data Distribution Service (DDS) standard has been selected
as the communications middleware to distribute information across the entire system. This paper describes the new
architecture of the control system and the middleware messaging, for handling the commands and telemetry based on
the use of the DDS standard.

The new observatories currently being built, upgraded or designed represent a big step up in terms of complexity (laser
guide star, adaptive optics, 30/40m class telescopes) with respect to the previous generation of ground-based telescopes.
Moreover, the high cost of observing time imposes challenging requirements on system reliability and observing
efficiency as well as challenging constraints in implementing major upgrades to operational observatories. Many of the
basic issues are common to most of the new projects, while each project also brings an additional set of very specific
challenges, imposed by the unique characteristics and scientific objectives of each telescope. Finding ways to share the
solution and the risk for these common problems would allow the teams in the different projects to concentrate more
resources on the specific challenges, while at the same time realizing more reliable and cost efficient systems. In this
paper we analyze the many dimensions that might be involved in sharing and re-using observatory software (e.g.
components, design, infrastructure frameworks, applications, toolkits, etc.). We also examine observatory experiences
and technology trends. This work is the continuation of an effort started in the middle of 2007 to analyze the trends in
software for the control systems of large astronomy projects.

The CTIO V. M. Blanco 4-m telescope is to be the host facility for the Dark Energy Survey (DES), a large area optical
survey intended to measure the dark energy equation of state parameter, w. The survey is expected to use ~30% of the
telescope time over 5 years and use a new 520 megapixel CCD prime focus imaging system: the Dark Energy Camera
(DECam). The Blanco telescope will also be the southern hemisphere platform for NEWFIRM, a large area infrared
imager currently being commissioned at the Mayall Telescope at KPNO. As part of its normal cycle of continuing
upgrades and in preparation for the arrival of these new instruments, the Blanco telescope control system (TCS) will be
upgraded to provide a modern platform for observations and maximize the efficiency of survey operations. The
upgraded TCS will be based on that used at the SOAR telescope and will be a prototype of the TCS to be used by LSST.
It will be optimized for programmed and queued survey observations, will provide extended real-time telemetry of site
and facility characteristics, and will incorporate a distributed observer interface allowing for on- and off-site
observations and real time quality control. Hardware modifications will include the use of absolute tape encoders and a
modern servo control and power driver systems.

Heidenhain position tape encoders are in use on almost all modern telescopes with excellent results. Performance of
these systems can be limited by minor mechanical misalignments between the tape and read head causing errors at the
grating period. The first and second harmonics of the measured signal are the dominant errors, and have a varying
frequency dependant on axis rate. When the error spectrum is within the mount servo bandwidth it results in periodic
telescope pointing jitter. This paper will describe an adaptive error correction using elliptic interpolation of the raw
signals, based on the well known compensation technique developed by Heydemann [1]. The approach allows the
compensation to track in real time with no need of a large static look-up table, or frequent calibrations. This paper also
presents the results obtained after applying this approach on data measured on the SOAR telescope.

An active tangent link system was developed to provide transverse support for large thin meniscus mirrors. The support
system uses six tangent links to control position and distribute compensating force to the mirror. Each of the six tangent
links utilizes an electromechanical actuator and an imbedded lever system working through a load cell and flexure. The
lever system reduces the stiffness, strength and force resolution requirements of the electromechanical actuator and
allows more compact packaging. Although all six actuators are essentially identical, three of them are operated quasi
statically, and are only used to position the optic. The other three are actively operated to produce an optimal and
repeatable distribution of the transverse load. This repeatable load distribution allows for a more effective application of
a look up table and reduces the demands on the active optics system.
A control system was developed to manage the quasi static force equilibrium servo loop using a control matrix that
computes the displacements needed to correct any force imbalance with good convergence and stability.
This system was successfully retrofitted to the 4.3 meter diameter, 100 mm thick SOAR primary mirror to allow for
more expeditious convergence of the mirror figure control system. This system is also intended for use as the transverse
support system for the LSST 3.4 meter diameter thin meniscus secondary mirror.

The Large Synoptic Survey Telescope (LSST) will be a large, wide-field ground-based telescope designed to obtain sequential images of the entire visible sky every few nights. The LSST, in spite of its large field of view and short 15 second exposures, requires a very accurate pointing and tracking performance. The high efficiency specified for the whole system implies that observations will be acquired in blind pointing mode and tracking demands calculated from blind pointing as well.
This paper will provide a high level overview of the LSST Control System (LCS) and details of the Telescope Control System (TCS), explaining the characteristics of the system components and the interactions among them. The LCS and TCS will be designed around a distributed architecture to maximize the control efficiency and to support the highly robotic nature of the LSST System. In addition to its control functions, the LCS will capture, organize and store system wide state information, to make it available for monitoring, evaluation and calibration processes. An evaluation of the potential communications middleware software to be utilized for data transport, is also included.

The CTIO V. M. Blanco 4-m telescope is to be the host facility for the Dark Energy Survey (DES), a large area optical
survey intended to measure the dark energy equation of state parameter, w, to a precision of ˜ 5%. The survey is
expected to take 5 years and use a new 520 megapixel CCD prime focus imaging system: the Dark Energy Camera
(DECam). In preparation for the arrival of DECam, we plan numerous upgrades to the telescope, including a new
telescope control system optimized for programmed and queued survey observations, modifications to the telescope
itself to improve reliability and performance, extended real-time telemetry of site and facility characteristics, and a
distributed observer interface allowing for on- and off-site observations and real time quality control. These upgrades
are specifically motivated by the scientific goals of the DES but will also improve community use of the telescope.

The 4.1-meter SOuthern Astrophysical Research (SOAR) Telescope mount and drive systems have been commissioned and are in routine operation. The telescope mount, the structure and its full drive systems, was fully erected and tested at the factory prior to reassembly and commissioning at the observatory. This successful approach enabled complete integration, from a concrete pier to a pointing and tracking telescope, on the mountain, in a rapid 3-month period. The telescope mount with its high instrument payload and demanding efficiency requirements is an important component for the success of the SOAR scientific mission. The SOAR mount utilizes rolling element bearings for both azimuth and elevation support, counter torqued sets of gear motors on azimuth and two frameless torque motors built into the elevation axles. Tracking jitter and its associated spectra, pointing errors and their sources, bearing friction and servo performances are critical criteria for this mount concept and are important factors in achieving the mission. This paper addresses the performance results obtained during the integration, commissioning, and first light periods of the telescope mount system.

Development of the 4.1 meter SOuthern Astrophysical Research (SOAR) Telescope is now complete. All baseline systems are in place and extensive commissioning activities have been performed with and without the primary optics installed in the telescope. The facility and dome have been under observatory operations and TCS control for a year of testing and tuning. The altitude over azimuth telescope mount was integrated on the mountain in a rapid 3-month period due to the complete assembly and testing performed at the factory prior to delivery. Early mount testing and successful integration into the Telescope Control System (TCS) without the optical system was accomplished on the sky through use of two separate small aperture telescopes fixed to the structure. One of these, the "feed telescope" was also pivotal in early testing of the calibration wavefront sensor and SOAR optical imager by directing focused light to these separate instruments. The SOAR optical system, with its 4.1 meter clear aperture, 100 cm thick, ULEtm primary mirror, its lightweight ULEtm secondary, and its fast tip tilt ULEtm tertiary has been delivered and installed in the telescope. This system was also assembled as an electrically connected system and individually optically tested under a visible interferometer at the factory enabling rapid integration and a short commissioning period on telescope. In this paper we present the project status, a summary of the commissioning period, and the performance data for the completed telescope and its major components.

The SOAR Telescope project has completed development of the Active Optical System (AOS) software system. This paper describes the two Computer Software Components (CSCs) that are part of the SOAR/AOS software. The first CSC is referred to as the Operations Control (OpCon) Software. The OpCon Software contains all of the software necessary for running and monitoring the Adaptive Optics Control System (AOCS). This includes the software to run the Primary Mirror Assembly (PMA), to command the Secondary Mirror Assembly (SMA) and the Turret Controller, to set the modes of the Tip/Tilt mirror, and to monitor and report status from the status data acquisition board. It includes the command and data interface to the Telescope Control System (TCS). It includes the AOCS state logic and the input routines for reading the database of command vectors. The second CSC is called the Database Generation (DBGen) Software. The DBGen Software contains the software that generates the database of PM force vectors and SM command vectors. This software uses either theoretical data or measured wavefront data to build the databases.
This paper focuses particularly on the PMA actuator control software. We describe the use of Nastran modeling data for initial deployment of the telescope and the concept for using actual measured data for calibration optimization. We also describe the software implementation designed to allow the actuator control system to meet its timing requirements during telescope slew and to meet the primary figure requirements during telescope observations.

The 4.1 meter Southern Astrophysical Research (SOAR) Telescope is now entering the operations phase, after a period of construction and system commissioning. The SOAR TCS implemented in the LabVIEW software package, has kept pace throughout development with the installation of the other telescope subsystems, and has proven to be a key component for the successful deployment of SOAR. In this third article of the SOAR TCS series, we present the results achieved when operating the SOAR telescope under control of the SOAR TCS software. A review is made of the design considerations and the implementations details, followed by a presentation of the software extensions that allows a seamless integration of instruments into the system, as well as the programming techniques that permit the execution of remote observing procedures.

The SOAR Telescope Project has developed a highly integrated Telescope and Observatory Control System, written in the LabVIEW graphical "G" language. A "plug-in" architecture and the ease of developing GUIs in LabVIEW has lead to a design and implementation that gives the operators flexibility, ease of use and a clear visual insight into the complex interactions of the many subsystems of a modern telescope. Care has been taken to abstract the many complexities into displays and controls that allows the operators to concentrate more on the functional operation of the telescope and observatory, and less on the intricacies of the various subsystems hardware. The User Interface includes many innovative features to make the operator?s job easier. Our process methodology for developing the TCS/OCS and continuous peer review/revision are enabling us to exceed SOAR's requirements and create a TCS/OCS that can easily be applied to other telescopes.

The SOAR Telescope is in the final phases of construction. Software development is progressing well, in accordance with installation of the telescope subsystems. Our original strategy, explored during the prototype phase, has been maintained and improved, resulting in a software package of great flexibility. This paper describes the implementation details that have proved to be most useful for the development of the SOAR TCS.

The SOAR telescope will begin science operations in 3Q 2003. From the outset, astronomers at all U.S. research universities will be able to use it remotely, avoiding 24+ hrs of travel, and allowing half-nights to be scheduled to enhance scientific return. Most SOAR telescope systems, detector array controllers, and instruments will operate under LabVIEW control. LabVIEW enables efficient intercommunication between modules executing on dispersed computers, and is operating-system independent. We have developed LabVIEW modules for remote observing that minimize bandwidth to the shared LAN atop Cerro Pachon. These include control of a Polycom videoconferencing unit, export of instrument control GUI's and telescope telemetry to tactical displays, and a browser that first compresses an image in Chile by a factor of 256:1 from FITS to JPEG2000 and then sends it to the remote astronomer. Wherever the user settles the cursor, a region-of-interest window of lossless compressed data is downloaded for full fidelity. As an example of a dedicated facility, we show layout and hardware costs of the Remote Observing Center at UNC, where instruments on SOAR, SALT, and other telescopes available to UNC-CH astronomers will be operated.

A Rapid Prototype and full development plan of the SOAR TCS is reviewed to show advances in: (1) Prototyping speed, which makes implementation and test of features faster than specification under older methods. This allows the development environment and prototype modules to become partners with and part of the specification documents. (2) Real-Time performance and reliability through use of RT Linux. (3) Visually Rich GUI development that allows an emphasis on `seeing' versus `reading'. (4) Long-Term DataLogging and Internet subscription service of all desired variables with instant recall of historical trend data. (5) A `plug-in' software architecture which enables rapid reconfiguration and reuse of the system and/or plug-ins utilizing LabVIEW graphical modules, a scripting language engine (in LabVIEW) and encapsulation of interfaces in `instrument-driver' style `plug-in' modules. (6) A platform- independent development environment and distributed architecture allowing secure internet observation and control via every major OS and hardware platform.

A low cost tip-tilt wavefront stabilization system has been put into operation on the Blanco 4-m telescope on Cerro Tololo. A light-weighted f/15 secondary mirror is driven by three commercial piezoelectric actuators. A dichroic at the Cassegrain focus separates optical reference and IR science beams. A steerable high-speed optical CCD sensor, coupled to a dedicated PC for control and image processing, provides positional feedback to the secondary. The IR field is reflected to one of several science sensors. We present a system description, initial performance measures at the telescope, and directions for future improvements.

The 4 m telescope at Cerro Tololo Inter-American Observatory has recently been fitted with an active optics system. As with the NTT and other active-optics telescopes, coma is corrected by tilting the secondary mirror while the other low-order aberrations are removed by deforming the primary mirror. The modifications to the telescope include a new computer- controlled collimation/focus unit for the secondary mirror, and the conversion to active control of the 33 axial supports for the primary mirror. The system works quite well, in spite of having been built at low cost and having to deal with an `old technology' thick primary mirror. We describe here the hardware and software control approach, along with the first results following installation.

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